The present invention relates to communication systems in general, and in particular to computer communication systems.
Despite the fact that a majority of individuals in the United States have access to one or more personal computers, most residences are not wired to take advantage of the high-speed communication or resource sharing capabilities of such computers. Most computer-to-computer or computer-to-peripheral communications take place over high-speed networking cables not found in most residences. As an alternative to rewiring existing homes with high-speed cables such as Ethernet, a standardized high-speed data transfer protocol called Home PNA is jointly being developed by companies such as 3Com, AMD, ATT, Compaq, Conexant, IBM, Intel, and Lucent. Home PNA allows computer systems to transmit and receive high-speed digital data over the existing telephone wires which are generally routed throughout a residence. Home PNA signals are transmitted in a frequency band that extends from 5.5-9.5 MHz in order to avoid conflict with other signals, such as DSL or voice signals, that may be simultaneously transmitted on the telephone wiring.
In the past, if a user wanted to be able to transmit and receive data from their computer, the computer had to be equipped with multiple interface cards. One card may be an analog modem for transmitting and receiving data in the voice band of a conventional telephone circuit. A DSL card is required to transmit and receive high-speed digital data on a set of telephone wires. Finally, to transmit and receive data on a Home PNA network, yet another interface card is required. Each of these cards typically includes an arrangement of filters that isolate data signals in a particular frequency band. The filters are primarily comprised of a number of analog components that are expensive to manufacture and align. To reduce the redundancy associated with having more than one individual interface card, there is a need for a single interface card that can facilitate transmitting and receiving digital data in a number of different frequency bands without the need for complex analog filter components.
The present invention is a single interface card that allows a computer to transmit and receive digital data in a number of frequency bands without the use of analog filter components. To transmit and receive data on conventional household telephone wiring, the interface card includes an isolation circuit that couples signals from the telephone wiring to the interface card. The output of the isolation circuit feeds a single analog-to-digital/digital-to-analog (AtoD/DtoA) converter. The output of the AtoD/DtoA converter feeds a digital splitter/combiner that utilizes digital signal processing or discrete digital logic to filter digital data into multiple frequency domains. Signals in a voice band from 0.1-4 kHz are supplied by the digital splitter/combiner to a PCM modem. Signals in the 85-500 kHz range are supplied to DSL circuitry. In addition, digital signals in the 5.5-9.5 MHz range are supplied by the digital splitter/combiner to Home PNA circuitry. The digital splitter/combiner allows a single card to be created with few or no analog filter components, as well as eliminates the need for multiple separate integrated circuits for processing each of the different frequency bands.